What guests see after entering the last 4 digits of their phone. Changes show up for them right away.
Airbnb: Calendar → your listing → Availability → Connect calendars → Import calendar → paste the link, name it "Kubo".
Booking.com: Extranet → Rates & Availability → Sync calendars → Add calendar connection → paste the link.
Agoda: YCS → Calendar → iCal / Calendar sync → Import → paste the link.
Platforms refresh imported calendars every few hours (Airbnb about every 2–3 hours), so a block takes a while to show up there. Keep this link private.